Most linear motion guide units used extensively in diverse fields of machinery such as semiconductor manufacturing equipments, various assembly machines, inspection instruments, medical gadgets, measurement instruments, and so on are needed in years to shrink them down as minuscule or tiny as permitted in construction, even with making sure of highly precise and smooth movement between components allowed to slide relatively to one another. Latest advanced linear motion guide units have been in pursuit of maintenance-free and especially miniaturization in construction, besides improvements in operational performance including high precision, fast travel, and so on. To meet with the micromechanical requirements as stated earlier, a variety of components and parts to build the linear motion guide unit is getting smaller in construction and less in their number to reduce the assembling steps as well as make any difference in dimension between mating parts less, which might occur in assembling steps, thereby making components or parts as integral as possible. Moreover, it has been needed to relieve the carriage of the slider from many chores including tiny hole-making operation, tiny tapping operation, tiny screw-driving operation, and so on. In summary, the linear motion guide units are now one of the elementary machines practically indispensable to every machine and correspondingly they are used in a wide range of sizes and versions. Nevertheless, modern advanced micromachines needs to further shrink the linear motion guide unit down in size, even with making certain of nimble sliding operation of the slider over the guide rail.
One version of the prior linear motion guide units is disclosed in the commonly assigned Japanese Patent Laid-Open No. 2001-12465, in which a guide rail is composed of a pair of lengthwise sides and a lengthwise bottom joining the sides together with one another along their lengthwise lower edges. With the prior linear motion guide unit recited just above, a slider is comprised of a carriage mostly accommodated in a lengthwise recess defined between widthwise opposing sides of the guide rail, end caps arranged on forward and aft ends of the carriage, one to each end, and end seals attached on the end caps, one to each cap, to seal clearances between the guide rail and the end caps. The end caps and end seals are tightened together to the carriage by means of machine screws, which are screwed into matching threaded holes made in the carriage.
With the prior linear motion guide unit constructed as stated earlier, the carriage is necessarily made therein with threaded holes that are used to fasten both the end caps having turnaround passages therein and the end seals on the forward and aft ends of the carriage. Thus, the prior linear motion guide unit recited earlier is remarkably complicated in construction and further has to go through some troublesome processes of tapping into the carriage in advance to hardening of the carriage, and precise fitting, combining and mating the associated parts or components together with one another to assemble the carriage with the end caps and end seals into a unitary slider. Tapping into the carriage is especially unfit for the tiny carriage, which would experience working, assembling, and so on to finish micromechanical linear motion guide units.
Another commonly assigned Japanese Patent Laid-Open No. 2002-227840 discloses a linear motion guide unit suited to be miniaturization, in which component parts to be combined with a carriage are reduced in number while the parts are assembled together in a snap-fit manner. The slider is comprised of a carriage made up of a major upper portion and side portions depending downwards from widthwise opposing edges of the major upper portion, and a composite member including end caps facing forward and aft ends of the carriage and a covering frame integral with the end caps. The composite member is composed of a first member and a second member adapted to fit over the first member from the outside. With the linear motion guide unit constructed as stated earlier, the composite member is brought into engagement with the carriage after first engaging parts or recesses in the forward and aft ends of the carriage have fit over or conform to their mating second engaging parts or projections in the first member of the composite member.
With the linear motion guide unit recited just above, formation of the first engaging parts or recesses in the carriage is needed to fit the composite member over the carriage. Thus, the carriage has to experience working operation to make the first engaging parts prior to hardening process of the carriage to make raceway grooves on steel material. This means that the prior linear motion guide unit recited is also complicated in construction and further unfit for working, assembling operation, and so on to finish micromechanical linear motion guide units.
Another version of the prior linear motion guide units is disclosed, for example in Japanese Patent Laid-Open No. H06-147222, in which a slider striding over a linear guide tack for movement is made up of first to third components. With the linear motion guide unit recited now, the first component includes forward and aft end caps and lengthwise intermediate members joined integrally with the end caps to provide sidewise outside lower portions to define return passages. The second components has a major portion made of metallic material having a lengthwise dimension corresponding to a load-carrying raceway and a return passage of a recirculating circuit where more than one rolling element is allowed to roll through there. The second component further has widthwise opposing ridges raised integrally downwards below the major portion over the lengthwise dimension equal with the overall length of the major portion to provide sidewise inside lower portions to define return passages. The third component is made of forward and aft blocks that are used to fit into forward and aft clearances left between the end caps of the first component and their associated lengthwise end surfaces of the second component, one to each clearance.
With the linear motion guide unit constructed as stated just earlier, tapping operation on the forward and aft ends of the major portion in the second component is needed to join the second component together with both the first and third components with using screws. Thus, the prior linear motion guide unit stated just above, as with other versions recited earlier, is also complicated in construction and further unfit for working, assembling, and so on to finish micromechanical linear motion guide units.
A further another version of the prior linear motion guide arrangement is disclosed in, for example Japanese patent No. 2936166, in which a guide rail having an axis is combined with a guide carriage movable on the guide rail in the direction of the axis, which runs on the guide rail with intermediacy of an endless rolling-element circuit. With the linear motion guide arrangement recited above, the guide carriage includes a guide carriage housing to form a positioning well into which a carriage member fits together with reversing bodies.
The linear motion guide arrangement constructed as stated earlier is needed to make the positioning well, and therefore is complicated in construction and further unfit for working, assembling, and so on to finish micromechanical linear motion guide units.